1. Field of the Invention
This invention relates to a recording/reproducing head, a recording/reproducing disk, and a recording/reproducing disk apparatus that employ the optically assisted magnetic (OAM) recording system that records information on a magnetic recording film or a magneto-optic recording film by means of a magnetic field and a beam spot and reproduces the information by means of a magnetic head, and relates more particularly to a recording/reproducing head, a recording/reproducing disk, and a recording/reproducing disk apparatus that realize high density recording, reduced cost, easy tracking control, and high speed seek operation.
2. Description of the Related Art
In the field of the hard disk drive (HDD) that is used for recording/reproducing data on a magnetic recording film by means of a magnetic head, the magnetic resistive sensor that utilizes the magnetic resistive effect for reproduction, namely the MR (Magnetoresistive) sensor as well as the high-sensitivity high-resolution GMR (Giant-magnetoresistive) sensor, have been developed (sensors including these sensors are termed collectively as magnetic sensor hereinafter), and as the result the recording density has been increased approximately 60% each year for recent several years. However, the limitation of surface density of approximately 30 Gbits/inch2 due to the Super Para-magnetic effect, namely the effect that the magnetization direction of a magnetic domain is reversed by the adjacent magnetization in the opposite direction based on the thermal fluctuation, has been revealed.
To solve the problem, OAM (Optically Assisted Magnetic) recording system has been proposed. This system involves a method in which the data is recorded on a magnetic recording film or a magneto-optic recording film by means of a magnetic field and a beam spot and the data is reproduced by means of a magnetic sensor such as a GMR sensor, wherein the magnetic film is heated by laser beam irradiation during recording and the data is recorded on the portion of the film where the magnetization magnitude is reduced. This system realizes the recording on a high magnetization magnetic film and prevents the flux reversal. An example of such a conventional recording/reproducing disk apparatus that employs the OAM recording system is described in a literature xe2x80x9cNikkei Electronics No. 734 (Jan. 11, 1999) p35xe2x80x9d.
FIG. 20 shows such a recording/reproducing disk apparatus. The recording/reproducing disk apparatus 1 is provided with a semiconductor laser 2 for emitting a laser beam 3, a polarized beam splitter 33 for separating the laser beam 3 emitted from the semiconductor laser 2 and the reflected beam from a recording/reproducing disk 21, a quarter wave plate 34 for converting the laser beam 3 from the semiconductor laser 2 to a circularly polarized beam, a condense lens 4xe2x80x2 for condensing the laser beam 3 from the semiconductor laser 2 that has passed through the polarized beam splitter 33 and the quarter wave plate 34, a semispherical SIL (Solid Immersion Lens) 5 for forming a beam spot 9a on a condensed surface 5b by condensing the laser beam 3 from the beam-condense lens 4xe2x80x2 incident from a semispherical incident surface 5a, a slider 31 for holding the SIL 5, a magnetic field modulation coil 10 provided, on the periphery of the beam spot 9a of the slider 31, and a magnetic sensor 11 having a GRM sensor.
When information is to be recorded by use of the apparatus 1 having the structure as described hereinabove, tracking is carried out based on the tracking mark (the term includes tracking groove in the present specification) for the beam spot formed on a recording/reproducing disk 8 to form a beam spot 9a on the condense surface 5b of the SIL 5, and then the near field wave 9b that leaks from the above-mentioned beam-condensed surface 5b is irradiated onto the magneto-optic recording film 8a on the recording/reproducing disk 8 to heat the film 8a and the information is recorded while the magnetic field is being modulated by means of the coil 10. In the case of the condensation by means of the SIL 5, though the near field wave is termed as the pseudo near field wave to discriminate it from the true near field wave because the transmitted beam and the near field wave are mixed near the condense surface 5b, these beams are not discriminated herein and they are referred as near field wave collectively because the near field wave plays a substantial role in condensation and the near field wave is used within a distance shorter than a fraction of the wavelength of the leakage beam. When the information is to be reproduced, tracking is carried out by use of the magnetic sensor based on the tracking marks formed on the recording/reproducing disk 8, that is, reproduction of the information is carried out by means of the magnetic sensor. According to the apparatus 1, the beam spot 9a can be fined in inversely proportional to the refractive index of the SIL 5, and minute recording magnetic domains having a width of approximately 0.3 micron are formed and high density recording is implemented.
However, according to the conventional recording/reproducing disk apparatus, because the tracking marks for the beam spot and the tracking marks for the magnetic sensor are formed respectively on the recording/reproducing disk, the recording density is restricted. Further, when additional fabrication processes for forming 2 kinds of tracking marks are needed, the conventional recording/reproducing disk apparatus results in higher cost.
The conventional recording/reproducing disk apparatus is disadvantageous in that the control system become complex when the tracking control is carried out by use of the tracking marks for the beam spot during recording and the tracking control is carried out by use of the tracking marks for the magnetic sensor during reproduction.
The tracking by use of the magnetic sensor is disadvantageous in that it is difficult to form a highly accurate tracking marks and to track the marks highly accurately due to leakage magnetic flux on the head side surface.
Further, because it is not considered that the track for beam spot tracking and the track for magnetic sensor tracking are closely formed, the seek operation between these two kinds of tracks is required for the transition from recording to reproduction (verify) and from reproduction to recording (correction and re-recording).
Another aspect of the disadvantage of the conventional recording/reproducing disk apparatus is caused from using an air-core coil for the magnetic modulation. The size of the coil should be minimized to be mounted on an optical head which is also minimized for the high density and high speed recording. However, to obtain the magnetic intensity required for recording, the number of turns of the coil should be increased, which causes the increase of the inductance, then the high speed modulation and the transfer rate is restricted. On the contrary, limiting the number of turns causes the insufficiency of the magnetic intensity, then the OAM is hardly carried out stably.
The present invention has been made in view of the above circumstances and provides a recording/reproducing head, a recording/reproducing disk, and a recording/reproducing disk apparatus which are capable of high density recording, cost reduction, easy tracking control, and high speed seek operation.
The present invention also provides a recording/reproducing head, and a recording/reproducing disk apparatus which are capable of high transfer rate and stable OAM recording.
According to the present invention, the recording/reproducing head and a recording/reproducing disk apparatus includes a laser beam emitting unit that emits a laser beam, a transparent condensing medium having a first surface which condenses the laser beam emitted from the laser beam emitting unit and a second surface on which the laser beam is condensed by the first surface as a beam spot near an end of the second surface, and a magnetic sensor disposed close to the end of the second surface, which detects an incident magnetic field.
With the above structure, the beam spot is formed near the end of the second surface of the transparent condensing medium, and therefore it is possible to shorten the distance between the beam spot and the magnetic sensor. As the result, tracking during recording and reproduction, it is possible to make the magnetic sensor to trace the track by the tracking of the optical sensor. Thus high speed seek operation is implemented.
The present invention further provides a recording/reproducing disk that is capable of optically assisted recording in which information is recorded by means of application of a magnetic field and irradiation of a near field wave spot and the information is reproduced by a magnetic sensor. Tracking marks for the near field wave spot are provided to be used in the recording and the reproduction.
With the above structure, the recording track can be increased because the tracking marks for the magnetic sensor is not provided, and thus the high recording density is implemented.
The present invention further provides a recording/reproducing disk apparatus having a recording/reproducing head that records information by means of application of a magnetic field and irradiation of a near field wave on a recording/reproducing disk and reproduces the information by a magnetic sensor. The apparatus has a tracking unit that tracks based on the tracking marks for the near field wave spot on the recording/reproducing disk during the recording and the reproduction.
With the above structure, the tracking marks for the magnetic sensor can be omitted because tracking is performed based on the tracking marks for the near field wave spot during recording and reproduction, and as the result the number of recording tracks can be increased and high recording density is implemented.
Another aspect of the present invention further provides a recording/reproducing head including a laser beam emitting unit that emits a laser beam, a transparent condensing medium having a condense surface on which the laser beam is condensed, a coil that applies a magnetic field, disposed near the position on which the beam spot is formed, a shading member with an aperture of a predetermined size disposed on the condense surface at the position where the beam spot is to be formed. The shading member is formed of highly permeable material.
With the above structure, the number of turns of the coil can be reduced, thus the inductance is decreased, then high speed modulation can be performed. At the same time, the magnetic intensity can be improved, then the OAM recording can be performed stably.